Room-temperature ferromagnetism in Mn-implanted TiO_2

摘要

TiO_2 single crystals were doped with Mn using the ion implantation technique at high doses leading to Mn concentrations of up to 7 at.% Mn. The Mn-doped TiO_2 orders ferromagnetically above room temperature. The magnetic moment of the as-implanted samples (0.3 μ_B per Mn) is reduced after thermal annealing at 400℃ under oxygen atmosphere due to a reduction of the oxygen deficiency. The moment recovers after annealing at higher temperatures reaching 0.4 μ_B per Mn which indicates the incorporation of Mn atoms on substitutional sites. Electron spin resonance measurements show two types of signals which are independent of the orientation of the magnetic field corresponding to Mn~(2+) and Mn~(2+)-O-Mn~(2+). In addition, four lines are strongly dependend on the orientation of the magnetic field and can be attributed to Mn~(4+).